/**
 * @license
 * Copyright (c) 2000-2005, Sean O'Neil (s_p_oneil@hotmail.com)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * * Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * * Neither the name of the project nor the names of its contributors may be
 *   used to endorse or promote products derived from this software without
 *   specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Modifications made by Analytical Graphics, Inc.
 */
//This file is automatically rebuilt by the Cesium build process.
define(function() {
    'use strict';
    return "attribute vec4 position;\n\
uniform vec4 u_cameraAndRadiiAndDynamicAtmosphereColor;\n\
const float Kr = 0.0025;\n\
const float Kr4PI = Kr * 4.0 * czm_pi;\n\
const float Km = 0.0015;\n\
const float Km4PI = Km * 4.0 * czm_pi;\n\
const float ESun = 15.0;\n\
const float KmESun = Km * ESun;\n\
const float KrESun = Kr * ESun;\n\
const vec3 InvWavelength = vec3(\n\
5.60204474633241,\n\
9.473284437923038,\n\
19.643802610477206);\n\
const float rayleighScaleDepth = 0.25;\n\
const int nSamples = 2;\n\
const float fSamples = 2.0;\n\
varying vec3 v_rayleighColor;\n\
varying vec3 v_mieColor;\n\
varying vec3 v_toCamera;\n\
float scale(float cosAngle)\n\
{\n\
float x = 1.0 - cosAngle;\n\
return rayleighScaleDepth  * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25))));\n\
}\n\
void main(void)\n\
{\n\
float cameraHeight = u_cameraAndRadiiAndDynamicAtmosphereColor.x;\n\
float outerRadius = u_cameraAndRadiiAndDynamicAtmosphereColor.y;\n\
float innerRadius = u_cameraAndRadiiAndDynamicAtmosphereColor.z;\n\
vec3 positionV3 = position.xyz;\n\
vec3 ray = positionV3 - czm_viewerPositionWC;\n\
float far = length(ray);\n\
ray /= far;\n\
float atmosphereScale = 1.0 / (outerRadius - innerRadius);\n\
#ifdef SKY_FROM_SPACE\n\
float B = 2.0 * dot(czm_viewerPositionWC, ray);\n\
float C = cameraHeight * cameraHeight - outerRadius * outerRadius;\n\
float det = max(0.0, B*B - 4.0 * C);\n\
float near = 0.5 * (-B - sqrt(det));\n\
vec3 start = czm_viewerPositionWC + ray * near;\n\
far -= near;\n\
float startAngle = dot(ray, start) / outerRadius;\n\
float startDepth = exp(-1.0 / rayleighScaleDepth );\n\
float startOffset = startDepth*scale(startAngle);\n\
#else // SKY_FROM_ATMOSPHERE\n\
vec3 start = czm_viewerPositionWC;\n\
float height = length(start);\n\
float depth = exp((atmosphereScale / rayleighScaleDepth ) * (innerRadius - cameraHeight));\n\
float startAngle = dot(ray, start) / height;\n\
float startOffset = depth*scale(startAngle);\n\
#endif\n\
float sampleLength = far / fSamples;\n\
float scaledLength = sampleLength * atmosphereScale;\n\
vec3 sampleRay = ray * sampleLength;\n\
vec3 samplePoint = start + sampleRay * 0.5;\n\
vec3 frontColor = vec3(0.0, 0.0, 0.0);\n\
vec3 lightDir = (u_cameraAndRadiiAndDynamicAtmosphereColor.w > 0.0) ? czm_sunPositionWC - czm_viewerPositionWC : czm_viewerPositionWC;\n\
lightDir = normalize(lightDir);\n\
for(int i=0; i<nSamples; i++)\n\
{\n\
float height = length(samplePoint);\n\
float depth = exp((atmosphereScale / rayleighScaleDepth ) * (innerRadius - height));\n\
float fLightAngle = dot(lightDir, samplePoint) / height;\n\
float fCameraAngle = dot(ray, samplePoint) / height;\n\
float fScatter = (startOffset + depth*(scale(fLightAngle) - scale(fCameraAngle)));\n\
vec3 attenuate = exp(-fScatter * (InvWavelength * Kr4PI + Km4PI));\n\
frontColor += attenuate * (depth * scaledLength);\n\
samplePoint += sampleRay;\n\
}\n\
v_mieColor = frontColor * KmESun;\n\
v_rayleighColor = frontColor * (InvWavelength * KrESun);\n\
v_toCamera = czm_viewerPositionWC - positionV3;\n\
gl_Position = czm_modelViewProjection * position;\n\
}\n\
";
});